1. Field of the Invention
The present invention relates to a semiconductor device having a filter function of reducing intensity of an electromagnetic noise generated from a data communication path. Moreover, the invention relates to an electric apparatus that exchanges data with a memory device via a semiconductor device having a filter function of reducing intensity of an electromagnetic noise generated from a data communication path.
2. Description of the Related Art
A mobile phone device has an electromagnetic compatibility (EMC) filter device provided in the data communication path between the CPU and the memory card. The EMC filter device prevents a high-frequency component of an electromagnetic noise generated from the data communication path from interfering with the electromagnetic wave which is used by the mobile phone. For example, Jpn. Pat. Appln. KOKAI Publications No. 2005-6471 and No. 2004-228713 disclose such a filter device.
Specifically, the EMC filter device is mounted in the data communication path formed between the CPU of the mobile phone device and the memory card. A level shifter device is mounted between the CPU and the EMC filter device.
The level shifter device has a function for adjusting both memory cards in the 1.8 V standard and the 3.0 V standard to the mobile phone device in the 1.8 V standard. Typically, the level shifter device has a buffer amplifier section for compensating voltage outputted for data communication. The buffer amplifier section is directly electrically connected to the EMC filter device.
The memory card currently stores data having comparatively large capacity such as music or image information. Therefore, a communication speed between the memory card and the mobile phone device tends to be increased.
However, when the communication speed between the memory card and the mobile phone device is increased, intensity of a high-frequency component of the electromagnetic noise generated from the data communication path is increased. As a result, even if intensity of the high-frequency component is reduced by the EMC filter, the high-frequency component still has sufficient intensity to obstruct transmission and reception of an electromagnetic wave for use in a telephone call and the like.
On the other hand, as a factor of reducing a filter characteristic of the EMC filter device, inductance is given, which is due to electrical connection between the EMC filter device and the level shifter device via ground.
This point is specifically described. The EMC filter device and the level shifter device are mounted on a mobile phone substrate. A terminal to be connected to ground in the EMC filter device is connected to ground on a package substrate, which configures the EMC filter device, via bonding wire.
Similarly, a terminal to be connected to ground in the level shifter device is connected to ground on a package substrate, which configures the level shifter device, via bonding wire. The ground of the EMC filter device is electrically connected to the ground of the level shifter device through wiring formed on the mobile phone substrate.
When the EMC filter device is electrically connected to the level shifter device via ground in this way, each connection path becomes long. Furthermore, since inductance of the bonding wire itself is large, a filter characteristic of the EMC filter device is reduced.
Therefore, a semiconductor chip configuring the EMC filter device is connected to the package substrate configuring the EMC filter device in a flip-chip manner via bumps. Thus, the terminal to be connected to ground in the EMC filter device is connected to the package substrate via bumps.
By connecting the EMC filter device in the flip-chip manner as above, bonding wire is not used. As a consequence, the electromagnetic noise can be further decreased by the EMC filter device.
By improving the filter characteristic of the EMC filter device in this way, a measure is taken for increase in intensity of the high-frequency component of the electromagnetic noise along with increase in data communication speed between the CPU and the memory card.
However, capacity of data stored in the memory card is considered to be more increased in the future. Therefore, a sufficient measure for the high-frequency component of the electromagnetic noise along with further increase in data communication speed is considered to be difficult only by improving the filter characteristic of the EMC filter device according to a technique in the prior art.